1. Technical Field
The present invention relates to a light emitting diode (LED).
2. Description of Related Art
LEDs are semiconductors that convert electrical energy into light. Compared to conventional light sources, LEDs have higher energy conversion efficiency, higher radiance (i.e., they emit a larger quantity of light per unit area), longer lifetime, higher response speed, and better reliability. LEDs also generate less heat. Therefore, LED modules are widely used as light sources in optical imaging systems, such as displays, projectors, and so on.
A typical LED commonly includes an N-type semiconductor layer, a P-type semiconductor layer, an N-type electrode, and a P-type electrode. The P-type electrode is located on the P-type semiconductor layer. The N-type electrode is located on the N-type semiconductor layer. Typically, the P-type electrode is transparent. In operation, a positive voltage and a negative voltage are applied respectively to the P-type semiconductor layer and the N-type semiconductor layer. Thus, holes in the P-type semiconductor layer and photons in the N-type semiconductor layer can enter the active layer and combine with each other to emit visible light. However, the material of the semiconductor layer is gallium arsenide, gallium phosphide, silicon carbide, or gallium nitride, thus an active layer is required to be located between the N-type semiconductor layer and the P-type semiconductor layer. The structure is complicate.
What is needed, therefore, is a light emitting diode that can overcome the above-described shortcomings.